The interest rate does not matter if no more income is being made. 

This is the stickiest one around here, they have a no more then 3 unrelated persons ordinances.

However, a commonly used benchmark is the 70% rule.The 70% rule suggests that to make a flip worth it, you should aim to purchase a property for no more than 70% of the after-repair value (ARV) minus the estimated renovation costs.

No mortgage or no more than one mortgage. 3. 10+ years of ownership.4.

https://www.biggerpockets.com/blog/short-term-rental-loans-a...Also - PS on the advice regarding getting a vacation home loan - if this is referrring to the conventional 2nd Home / Vacation Home Loan (10% Down Loan) - I'd be very careful here, these are not supposed to be for STR investment properties (you are required to rent it out no more than half the year, not utilize prop management, ec.) - which doesn't sound like your plans for this investment

If a tenant is substantially under market, I may exceed that 5% mark but probably raise it by no more than maybe 10% max.

He even had former employees hire the contractors, so when he didn't pay them, they couldn't sue him but ended up suing is poor employees.He has bragged about never being able to be traceable because he sets up his LLCs in such a way he can operate without legal ramifications,This man has no moral compass and has stolen the retirements of so many people.He did all of this so he could fund his new syndication business MENACE CON, with his other partners Nicholas Trevillian and Jason Von Payne...

every thing he was doing seems to end around 6/2009 or so and no more blogs or his site are updated

They can't force you to accelerate payments, but they can say "no more" and cancel any further draw-downs. 

No more than you should become a master electrician, master plumber, HVAC tech,  insurance agent, loan officer, and maybe other licensed people.